Modifying the shape and color of hair is an important area of modern cosmetics. Consumers make use of color-modifying agents to obtain fashionable coloring of hairstyles or to conceal grayed or even white hair with fashionable or natural color shades.
Depending on the requirements placed on the coloring or color modification, a person skilled in the art is aware of various systems for providing color-modifying cosmetic agents, in particular for the skin or keratin-containing fibers such as for example human hair.
“Oxidation coloring agents” are used to achieve permanent, intense colorings with corresponding fastness properties. Such coloring agents conventionally include oxidation dye precursors, i.e. “developer components” and “coupler components”. Under the influence of oxidizing agents or of atmospheric oxygen, the developer components develop the actual dyes through action with one another or through coupling with one or more coupler components. Oxidation coloring agents are distinguished by intense, excellent and long-lasting coloring results. A mixture of a relatively large number of oxidation dye precursors must, however, normally be used if natural looking colorings are to be obtained; furthermore in many cases, substantive dyes are additionally used for shading purposes. Despite their advantageous coloring characteristics, oxidative hair coloring agents are associated with disadvantages for users. In particular, it is suspected that some common oxidation dye precursors, including p-phenylenediamine, have an irritant action on some consumers and consequently cause sensitization or even allergic reactions. There is therefore still a requirement to achieve further improvements in these substances with regard to their physiological acceptability profile. Numerous compounds have been researched during the search for replacement substances, but many suffer from applicational problems, in particular inadequate gray coverage capacity. Moreover, despite highly sophisticated coloring systems already having been developed, there is still a need for coloring systems which achieve excellent luminosity and intensity of the colorings while also having a very good durability and excellent homogeneity.
It is therefore desirable to reduce the above-stated disadvantages of oxidative hair coloring agents, and to provide coloring agents that impart to the hair intense colorings with elevated colorfulness and with good resistance to external influences, in particular with good light fastness and washing fastness, which do not suffer from color attenuation or color shifts even after repeated shampooing of the hair. It is further desirable that colorings should have the least possible selectivity, i.e. achieve maximally homogeneous and uniform coloring results on differently pretreated hair. The coloring agents should moreover have a toxicologically advantageous profile.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.